Without oestrus synchronisation

the use of Al in beef cows at pasture is not practical Controlled breeding in cattle COLIN PENNY OESTRUS synchronisation is a useful technique in cattle practice as it allows the use of fixed-time artificial insemination (Al) or improved heat detection efficiency. It can also be used to prepare donor and recipient cattle in embryo transfer programmes. As synchronisation techniques have improved, the number of beef cattle being served by Al has steadily increased. Not only does oestrus synchronisation with fixed-time Al eliminate the practical problems of heat detection in beef cattle, it also allows the use of superior, easy-calving sires. Until recently, oestrus synchronisation and fixed-time Al, while often used with replacement dairy heifers, was seldom used in lactating dairy cows in the UK as results tended to be poor compared to Al to observed heats. However, interest in synchronising oestrus in dairy cows has increased with the introduction of improved techniques utilising combinations of gonadotrophin releasing hormone and prostaglandin. The theory and current methods of oestrus synchronisation for fixed-time Al in cattle are briefly reviewed in this article. PHYSIOLOGY OF THE OESTROUS CYCL